1. Field of the Invention
The present invention relates to a traveling wave tube, and more particularly to a traveling wave tube that is suitable for use in an antenna mounted on a satellite or in a transmitting device that employs a phased-array antenna.
2. Description of the Related Art
In the interest of minimizing heat loss in the collector and thus raising the efficiency of traveling wave tubes that are mounted in artificial satellites or traveling wave tubes that are used in phased-array antennas, a multistage collector structure is adopted in which the collector electrodes are divided into a plurality of units.
In a traveling wave tube having this type of multistage collector structure, different voltages are applied to the collector electrodes of each stage, and electron beams having a velocity distribution as a result of interaction with a high-frequency wave are discriminated and acquired according to the velocity of each.
FIG. 1 is a side view showing an example of the construction of a traveling wave tube, and FIG. 2 is schematic sectional view showing the structure of a collector in the traveling wave tube shown in FIG. 1 showing the relation between the high-voltage leads and the insulating ceramic parts. Further, FIG. 3 is a sectional view showing the construction of an insulating ceramic part that is shown in FIG. 2. FIG. 2 shows a state in which high-voltage leads are routed through the lower-most portion of the insulating ceramic parts, but when four high-voltage leads pass through an insulating ceramic part as shown in FIG. 3, the high-voltage leads are not actually arranged at the lowermost portion but at positions that are slightly higher.
As shown in FIG. 1, the traveling wave tube is made up by: electron gun 50 having cathode 51 for emitting an electron beam; slow-wave circuit unit 60 made up by, for example, helix 61; magnetic focusing unit 70 made up by a periodic magnetic field generation device; input unit 80 for receiving the high-frequency signal that is the object of amplification; output unit 90 for outputting the high-frequency signal that has been amplified; and collector 100 of multistage collector structure.
In this construction, the electron beam that is emitted from cathode 51 advances inside helix 61 while interacting with the high-frequency signal that has been received from input unit 80. A high-frequency signal that has been amplified by interaction with the electron beam is then outputted from output unit 90. The electron beam has an energy distribution, is applied to collector 100, and is acquired at each collector electrode of collector 100.
As shown in FIG. 2, collector 100 of a traveling wave tube of the prior art is a structure in which a plurality of collector electrodes (four stages in FIG. 2) 11 are each bonded and secured by insulating ceramic parts 12 in the radial direction of vacuum envelope 13 that is composed of metal. High-voltage leads 14 are connected to each collector electrode 11 to supply prescribed voltages from the outside, and these high-voltage leads 14 are routed to the outside through holes that are provided in insulating ceramic parts 12.
As shown in FIG. 3, insulating ceramic parts 12 are of a construction formed in a cylindrical shape having uniform thickness in the radial direction so as to maintain a prescribed insulating capacity between vacuum envelope 13, which is connected to the ground potential, and collector electrodes 11, to which high voltages are applied; and in which a plurality of holes 15 are formed for routing the above-described high-voltage leads 14. The central axis of the inside diameter substantially coincides with the central axis of the outside diameter of these insulating ceramic parts 12.
In collector 100 of multistage collector structure, one high-voltage lead 14 passes through insulating ceramic part 12 that supports the first-stage collector electrode (C1 in FIG. 2), and two high-voltage leads 14 pass through insulating ceramic part 12 that supports the second-stage collector electrode (C2 in FIG. 2). Further, three high-voltage leads 14 pass through insulating ceramic part 12 that supports the third-stage collector electrode (C3 in FIG. 2), and four high-voltage leads 14 pass through insulating ceramic part 12 that supports the fourth-stage collector electrode (C4 in FIG. 2). In other words, high-voltage leads 14 do not pass through all of holes 15 provided in insulating ceramic parts 12. Nevertheless, the same number of holes are provided at the same positions such that the same insulating ceramic parts 12 can be used at any stage in collector 100 of the prior art.
In addition, collector 100 shown in FIG. 2 is a construction having an exhaust pipe attached (not shown in the figure), this exhaust pipe normally being affixed in an upper location of FIG. 2, and holes 15 for high-voltage leads in insulating ceramic parts 12 are therefore all formed on the lower side, as shown in FIG. 3.
In recent years, however, there has been an ever-increasing demand for lighter and more compact traveling wave tubes for installation in artificial satellites or phased-array antennas.
In the collector in the above-described traveling wave tube, however, the thickness of the insulating ceramic parts in the radial direction must be equal to or greater than a prescribed thickness depending on the dielectric strength of the insulating ceramic material in order to maintain an insulative property between each of the high-voltage leads and between the collector electrodes and the vacuum envelope.
Reducing the thickness of insulating ceramic parts having holes for routing high-voltage leads has therefore been problematic, and it has been impossible to meet the demand for greater compactness using the construction of the prior art.
It is an object of the present invention to provide a traveling wave tube in which the diameter of the vacuum envelope is reduced to achieve greater compactness.
To achieve the above-described object, the insulating ceramic parts for insulating the collector electrodes and vacuum envelope in the traveling wave tube of the present invention are formed in a cylindrical shape in which the central axis of the inner diameter diverges from the central axis of the outer diameter. The traveling wave tube of the present invention is further constructed such that holes are provided in those portions having greater thickness in the radial direction, and the high-voltage leads for supplying prescribed voltages to the collector electrodes are routed through these holes.
By means of the above-described construction, the diameter of the vacuum envelope can be made smaller than in the prior art while maintaining a prescribed insulative property between each of the high-voltage leads as well as between the collector electrodes and the vacuum envelope.
A traveling wave tube that is more compact that the prior art can therefore be obtained, and in particular, the use of the traveling wave tube of the present invention in a system in which a multiplicity of antenna elements are arranged, such as in phased-array antenna, contributes greatly to making the system more compact.
The above and other objects, features, and advantages of the present invention will become apparent from the following description with reference to the accompanying drawings, which illustrate examples of the present invention.